Coiled tubing apllication having vibration-based feedback

ABSTRACT

A method of performing a coiled tubing application using feedback includes conveying a coiled tubing string along a borehole and obtaining vibration measurement data based on vibrations within the coiled tubing string. The method further includes providing, during the coiled tubing application, feedback based on the vibration measurement data. The method further includes using a mechanical controller to adjust a variable element of the coiled tubing application based on the feedback.

BACKGROUND

Exploring, drilling, and completing hydrocarbon wells are complicated,time consuming, and expensive endeavors. As such, the hydrocarbonrecovery industry often emphasizes well access. Specifically, access toa well is important for monitoring its condition and maintaining itsproper health. Such access to the well is often provided by way of wellaccess lines such as coiled tubing.

Well access lines may be configured to deliver interventional ormonitoring tools downhole. In the case of coiled tubing and othertubular lines, fluid may also be introduced downhole. Coiled tubing isparticularly well suited for being driven downhole through a horizontalor tortuous well, to depths of perhaps several thousand feet, by aninjector at the Earth's surface.

When performing coiled tubing applications, it is common to use variousforms of impact tools to free stuck tools, clean out debris, etc. A bitmay even be attached to the coiled tubing for an alternative drillingapplication. However, it is not normally known what force these devicesare delivering and what their impact might be on other devices in thecoiled tubing string. Because these important variables in theapplications are unknown, operators are unsure of the reasons forsuccess or failure in a particular application thus resulting in aninability to credibly predict whether an application will be successfulbefore committing resources to it. Even if experience has shown that aparticular course of action will be successful in eliminating abnormalbehavior during a coiled tubing application, because of the unknownnature of the forces acting on the coiled tubing, operators cannot saythat such action is not wasteful of resources, i.e., inefficient.

BRIEF DESCRIPTION OF THE DRAWINGS

Accordingly, systems and methods of adjusting a variable element of acoiled tubing application based on vibration-based feedback aredisclosed herein. In the following detailed description of the variousdisclosed embodiments, reference will be made to the accompanyingdrawings in which:

FIG. 1 is a contextual view of an illustrative coiled tubing environmentfor a milling application;

FIG. 2 is a contextual view of an illustrative coiled tubing environmentfor a stuck tool application and a clearing debris application;

FIG. 3 is a contextual view of an illustrative coiled tubing environmentfor a perforation application, extended reaching application, andformation fluid detection application; and

FIG. 4 is a flow diagram of an illustrative method of adjusting avariable element of a coiled tubing application based on feedback.

It should be understood, however, that the specific embodiments given inthe drawings and detailed description thereto do not limit thedisclosure. On the contrary, they provide the foundation for one ofordinary skill to discern the alternative forms, equivalents, andmodifications that are encompassed together with one or more of thegiven embodiments in the scope of the appended claims.

NOTATION AND NOMENCLATURE

Certain terms are used throughout the following description and claimsto refer to particular system components and configurations. As one ofordinary skill will appreciate, companies may refer to a component bydifferent names. This document does not intend to distinguish betweencomponents that differ in name but not function.

In the following discussion and in the claims, the terms “including” and“comprising” are used in an open-ended fashion, and thus should beinterpreted to mean “including, but not limited to . . . ”. Also, theterm “couple” or “couples” is intended to mean either an indirect or adirect electrical or physical connection. Thus, if a first devicecouples to a second device, that connection may be through a directelectrical connection, through an indirect electrical connection viaother devices and connections, through a direct physical connection, orthrough an indirect physical connection via other devices andconnections in various embodiments.

In the following discussion and in the claims, “vibration profile” meansa collection of ranges for the measurements of vibrations sensors in acoiled tubing application. One or more vibration sensors reportingmeasurements outside of their corresponding range indicates abnormalbehavior for the coiled tubing application. All vibration sensorsreporting measurements inside their corresponding range indicate normalbehavior for the coiled tubing application.

DETAILED DESCRIPTION

The issues identified in the background are at least partly addressed bysystems and methods of adjusting a variable element of a coiled tubingapplication based on feedback. During coiled tubing applications,vibrations within the coiled tubing string may indicate any number ofproblems if the vibration characteristics are not within normaloperating ranges that make up a vibration profile associated with thecoiled tubing applications. Such vibrations may include longitudinal oraxial vibration, torsional vibration, and lateral vibration, and theidentification of the problems based on the vibration characteristicslead to solutions that may not only increase the efficiency of coiledtubing applications but save the applications from failure. The problemsmay be identified based on feedback of the status of the coiled tubingapplications, and the solutions may include adjusting one or morevariable elements of the coiled tubing applications. For example, in astuck-tool application, a variable element such as the flow rate offluid pumped through the coil tubing may be adjusted by a mechanicalcontroller such as a valve that increases or decreases the flow rate byopening and closing respectively. As another example, in a millingapplication, a variable element such as bit rotational speed may beadjusted by a mechanical controller such as a bit motor. In this way,many variable elements of many applications may adjusted. The variableelements may be adjusted in response to an operator command orautomatically, i.e. without human input, based on the feedback.

The disclosed systems and methods for adjusting a variable element of acoiled tubing application based on feedback are best understood in termsof the context in which they are employed. As such, FIG. 1 shows acontextual view of a coiled tubing environment including a feedbacksystem 100. The system 100 includes a coiled tubing string 54, which mayinclude coiled tubing coupled with a bottomhole assembly made up ofvarious subs 64 and tools 65. The coiled tubing is pulled from a spool52 by a tubing injector 56 and injected into a borehole 62 through apacker 58 and a blowout preventer 60. In this way, the coiled tubingstring 54 is conveyed along the borehole 62. As shown, the borehole 62initially is vertical. However, as detailed further below, the borehole64 may be of fairly extensive reach eventually turning horizontal.Additionally, directional drilling may result in a tortuous boreholewith many bends and turns.

The coiled tubing may be a continuous length of steel, alloy steel,stainless steel, composite tubing, or other suitable metal or non-metalmaterial that is flexible enough to be wound on the spool 52 fortransportation, and the spool 52 itself may be located on a coiledtubing truck for mobility. Due to the relative lack of joints, it isadvantageous to use coiled tubing when pumping chemicals downhole.

In the borehole 62, the coiled tubing string 54 includes a supervisorysub 64 and one or more tools 65 coupled to the coiled tubing 54 thatmake up the bottomhole assembly. The supervisory sub 64 may controlcommunication between uphole and downhole elements, and may also controlcommunication between downhole elements such as the one or more tools 65by providing a common clock, power source, communication bus, and thelike. The tools 65 may be subs, or other sections of the coiled tubingstring 54, that perform functions particular to a coiled tubingapplication. For example, in a perforation application the tools 65 mayinclude a perforation tool including perforating guns and the like. Asanother example, in a milling application the tools 65 may include amilling tool including a bit. Coiled tubing applications may beperformed offshore as well.

The system 100 also includes a data processing system 66, which may becoupled to an uphole interface 67 at the surface by a wired connectionor wireless connection, and may periodically obtain measurement datafrom the uphole interface 67 as a function of position and/or time. Theuphole interface 67 may communicate with the supervisory sub 64, tools65, and/or the computer system 66 and may enable communication betweenuphole and downhole elements. For example, mud pulse telemetry, acoustictelemetry, and the like may be used to provide communications from thesupervisory sub 64 to the uphole interface 67. Among other things, thedata processing system 66 processes data received from the upholeinterface 67, or the supervisory sub 64 and/or the one or more tools 65directly, and generates a representative display for the operator toperceive. Software (represented by information storage media 72) may runon the data processing system 66 to collect the data and organize it ina file or database stored on non-transient information storage media.Specifically, one or more processors coupled to memory may execute thesoftware and perform any appropriate action described below. Thesoftware may respond to user input via a keyboard 70 or other inputmechanism to display data as an image or movie on a monitor 68 or otheroutput mechanism. The software may process the data to optimize coiledtubing applications using feedback as described below, and the dataprocessing system 66 may send command signals to adjust a variableelement based on the feedback. In at least one embodiment, the dataprocessing system 66 is located downhole within a housing able toprotect the system 66 from the harsh downhole environment. In anotherembodiment, processors both at the surface and downhole may worktogether or independently to obtain, store, and process measurementdata. The supervisory sub 64 and/or the tools 65 may include suchdownhole processors.

The system 100 further includes one or more vibration sensors 90 coupledto the coiled tubing string. As shown, the vibration sensors are locatedon the supervisory sub 64, tool 65, and the coiled tubing, but one ormore vibration sensors may be located anywhere on the coiled tubingstring 54. For example, the vibration sensors 90 may be located oneither side of a downhole element, such as a particular tool, in orderto pinpoint the direction in which vibration waves travel at thatlocation of the coiled tubing string. The vibration sensors 90 measurevibrations within the coiled tubing string 54 during the coiled tubingapplication by measuring the characteristics of vibration wavestraveling through the string 54. For example, amplitude, frequency, andthe like may be measured. A vibration sensor 90 may include a tri-axialaccelerometer that senses three directional components of the vibrationwaves (one for each coordinate axis), a piezoelectric accelerometer,magnetometers, Hall Effect devices, and the like. The vibration sensors90 may measure or monitor lateral vibration, longitudinal vibration, andtorsional vibration.

By measuring the vibration characteristics, downhole conditions such asstress, load, frictional resistance, and the like may be monitored on anongoing basis. The vibration sensors 90 may be used to collect and relayvibration measurement data to the uphole interface 67 and/or dataprocessing system 66 for analysis of ongoing conditions during a coiledtubing application. Depending on the coiled tubing application,vibration sensors 90 at different locations will be relevant tomonitoring downhole conditions, and irrelevant sensors 90 may beexcluded from the comparison with the vibration profile. For example, ina milling application, the vibration sensor 90 closest to the distal endof the coiled tubing string 54 will be most relevant, whereas in aperforation application, the vibration sensor 90 closest to theperforation gun will be the most relevant. In this way, the datareported by the vibration sensors 90 may be weighted according torelevance. The weight may impact the significance attributed to thevibration measurement data when the vibration measurement data iscompared with a vibration profile.

For purposes of illustration of the concepts herein, relative terms of“low,” “medium” and “high” acceleration vibration measurements are usedherein. Such terms are not intended to reflect any specific values, asthe quantitative measurements will be recognized to those skilled in theart to be variable depending on the coiled tubing string utilized andthe components therein. For example, in terms of actual forcesexperienced, in many operational situations the axial acceleration onthe coiled tubing string 54 is generally on the order of 0.1 g; but itcan exceed 100 g for short time intervals (for example, a fewmilliseconds); and the lateral shock can exceed 1,000 g. Hence, inabsolute forces, low vibration might be characterized, for example, by amean vibration axial vibration level less than about 0.1 g with peaks onthe order of 1 g for a few ms, and cross-axial vibration less than about1 g with peaks no larger than 10 g. These thresholds may changedepending upon the application.

Similarly, high vibration might be characterized, for example, as avibration in which either the axial vibration exceeds 1 g on average, ithas peak accelerations exceeding 100 g, (for example, for 1 or moretimes per second), the lateral vibration exceeds 10 g on average, or thelateral vibration has peaks exceeding a few hundred g one or more timesper second. Medium level vibration could then, in this example, becharacterized by anything between those two states. These thresholdsalso may change depending upon the application. For clarity, however,the above examples are only examples, and are representative only ofabsolute forces; and thus actual measured vibration forces may besubstantially different from the example values, depending on themeasurement system and the coiled tubing string 54 characteristics. Thethresholds and baseline values used herein may be determined frommodeling, previous experience, or measurement during the coiled tubingapplication itself.

Considering a general coiled tubing application (specific coiled tubingapplications are discussed below), the one or more processors of thedata processing system 66 obtain vibration measurement data from thevibration sensors 90 (e.g. located on the bottomhole assembly) andprovide feedback during the coiled tubing application based on thevibration measurement data. The one or more processors may continuouslyprovide, over a period of time, feedback based on changing vibrationmeasurement data resulting from adjusting the variable element.Specifically, the system 100 includes a mechanical controller, and thecontroller adjusts a variable element of the coiled tubing applicationbased on the feedback. The mechanical controller may be actuatedmechanically, electrically, hydraulically, and the like. The controllermay continuously adjust the variable element based on the feedback untilthe vibration measurement data conforms to a profile associated with thecoiled tubing application. For example, in a stuck-tool application, amechanical controller such as a valve 61 increases or decreases fluidflow rate by opening and closing respectively. Although such a valve 61is shown downhole here, the valve may also be located at any point alongthe path in which such fluid circulates including at the surface. Avibration sensor 90 near the valve reports a low vibration that is outof the range of the vibration profile of a stuck-tool application. Next,the valve 61 opens wider to increase the fluid flow rate to help freethe stuck tool, and the vibration measurement data is again comparedwith the vibration profile. If the vibration sensor 90 reports datawithin the vibration profile, then no further action need be taken. Ifthe vibration sensor 90 reports data still outside the vibrationprofile, the valve 61 may be further widened until the vibration profilethreshold is reached for that particular sensor. Such adjustment mayoccur automatically, i.e., without human input. In at least oneembodiment, the feedback occurs in real-time.

Some examples of coiled tubing applications are milling, extendedreaching, freeing a stuck tool, clearing debris, perforation, formationfluid detection, and the like. During milling operations, a milling bitor similar downhole cutting tool on the coiled tubing string 54 is usedto cut and remove material from equipment or tools located in theborehole. As the coiled tubing is advanced downhole, it encountersfrictional resistance to continued advancement. Ultimately, suchresistance may halt the continued advancement of the coiled tubing. Thisresistance may be identified by a vibration sensor 90 sensing sinusoidalbuckling in the vertical section of the borehole which eventually risesto the level of helical buckling at the elbow or heel of the borehole ifit transitions to a lateral section. That is, vibrations that areprevalent throughout the advancing tubing begin to cease as the tubingbecomes stuck and immobile due to the buckling. This marked decrease inamplitude, greater than about a 10% threshold, may be detected by avibration sensor 90 located at the bottomhole assembly. Accordingly, amechanical controller such as injector may adjust the force on thecoiled tubing string 54 until the vibration sensor 90 indicates that thevibration measurement data is within the threshold again. In this waythe feedback may also include milling efficiency, the variable elementmay include force on the coiled tubing string, bit rotational speed,force on bit, bit type, or flow rate of fluid pumped through the coiledtubing, and the mechanical controller may include a motor coupled to thebit, a bit selector that switches out bits automatically, or a valverespectively. Specifically, these mechanical controllers may adjust thevariables such that vibration measurement data is within a millingvibration profile.

FIG. 2 is a partial contextual view of the system 200 of feedback incoiled tubing environments illustrative of stuck tool and clearingdebris applications. For clarity, the depiction and description of thedata processing system is not repeated. When trying to run into aborehole 10, understanding the vibration and load forces may provide theoperator on the surface information to avoid situations that would causethe cutting tool 22 to get stuck, and may also provide information ontargeting debris with a cutting tool 22. For example, a whipstock 20 maybe set to divert the coiled tubing string 16 such that a cutting tool22, including a bit attached to the end of the coiled tubing string 16,targets debris to be cleared after cutting by borehole fluid. Of course,the coiled tubing string 16 may also be diverted to avoid debris aswell. As the flow rate and/or pressure of fluid within the coiled tubingstring 16 increases, a motor 30 is actuated and turns the cutting tool22. A hydraulic anchor 38 and whipstock 20 have been oriented and set inposition using the coiled tubing string 16, and sufficient torquecreated by the motor 30 shears any coupling between the whipstock 20 andthe coiled tubing string 16. The cutting tool 22 begins to turn, and isguided at an angle to the borehole 10 by the whipstock 20. As the coiledtubing string 16 is further lowered downhole, the cutting tool 22 cutsat an angle through the casing 14 and creates an angled exit 36therethrough. In some embodiments, the borehole 10 may not be cased,however cutting an angled exit applies to an uncased borehole as well.

By adjusting the flow rate, e.g. with a valve 82, the actuation of themotor 30 may be adjusted based on vibration measurement data collectedby vibration sensors 90 in order to free stuck tools and clear debris.Vibration sensors 90 may be placed at any location along the coiledtubing string 16. For example, as shown the vibration sensors are placedon either side of the motor 30 as well as between the motor 30 and thecutting tool 22. The difference between the measurements obtained byeach sensor 90 may be used to identify abnormal behavior duringcomparison with a vibration profile.

Also, the system 200 may prevent stuck tools in addition to freeingstuck tools. Specifically, the speed of coiled tubing injection isknown, but the actual speed of the bottomhole assembly may not be known.However, with the addition of tri-axial accelerometers for vibrationsensing, the actual trajectory of the bottomhole assembly may bedetermined and used as feedback. Here, the mechanical controllerincludes the injector, which controls the speed at which the tubing isinserted and the force used for insertion. By using the feedback, theinjector provides smoother travel through the wellbore and reduction inthe possibility of sticking. In at least one embodiment, a load cellsensor is incorporated into the feedback to detect when the bottomholeassembly has come into contact with a wellbore obstruction.

FIG. 3 is a cross-sectional view of an illustrative, fractured borehole302. The illustrative borehole 302 has been fully drilled, all drillingequipment has been removed, and the borehole 302 has been cased withcasing 304 and cemented to sustain the structural integrity andstability of the borehole 302. The borehole 302 is formed within thetarget formation 300, which extends beyond the limited scope with whichit is represented in FIG. 3. The target formation 300 may includemultiple layers, each layer with a different type of rock formation,including the hydrocarbon-containing target formation within which theborehole may extend horizontally for some distance. The coiled tubingstring 320 includes a perforation tool 322 that creates multipleperforations 306 through which a fracturing fluid, such as water, isinjected with high pressure into the target formation. Thishigh-pressure fluid injection creates and opens fractures 308 thatextend laterally through the target formation. The high pressure fluidmay contain additional chemicals and materials, such as a proppantmaterial (e.g., sand) that maintains the structural stability of thefractures and prevents the fractures 308 from fully collapsing.Typically, the horizontal portions of the borehole are drilled generallyparallel to the direction of maximum stress, causing the fractures 308to propagate generally perpendicular to the borehole. (As fractures tendto propagate perpendicular to the direction of maximum stress, suchpropagation may be expected to occur at a predictable angle from theborehole axis when the borehole is not aligned with the maximum stressdirection.) The overlying and underlying formation layers tend to resistfracture propagation, consequently fractures tend to propagate laterallywithin the target formation, to a length that depends on the rate andvolume of the injected fracturing fluid. Thus each fracture 308 has alength 310 relative to the casing 304. Each fracture 308 also has aninitiation location 314 determined by the perforation position, which istypically measured relative to the distal end of the borehole 302. Whereregular spacing is employed, the perforations (and hence the fractureinitiation points) have a fixed spacing 312 between them. Thoughrepresented in the figures as generally planar, the actual fractures 308may be represented as a branching network having a form and size thatdepends not only on the properties of the fracturing injection stream,but also on the nature of the rocks and formation materials of thetarget formation. Accordingly, fracture shapes and sizes are not limitedto those shown in FIG. 3.

The impact of firing a perforating gun from the perforation tool 322 maybe measured by vibration sensors 90. Additionally, determining that theperforating gun has fired is non-trivial due to noisy and chaoticdownhole conditions. A mechanical controller, such as a lockout switch,may prevent other activities from occurring if the vibration sensor 90has not detected vibrations associated with the firing of theperforating gun. For example, activities such as injection of fracturingfluid, a sand cleanout, pulling out of hole, and moving to anotherperforation location may be prevented.

Extended reach boreholes refer to long horizontal boreholes. The aims ofan extended reach borehole are to reach a larger area from one surfacedrilling location and to keep the borehole within a reservoir for alonger distance in order to maximize its productivity and drainagecapability. It is a challenge to clean such a borehole, manage themechanical loads on the coiled tubing string 320, and manage downholepressure. As such, the vibration sensors 90 may measure characteristicsindicative of excess loads and pressures, such as buckling, andmechanical controllers such as injectors or valves may adjust the forceon the coiled tubing string 320 or flow rate of fluid pumped through thecoiled tubing to alleviate loads, pressure, and the like. Additionally,in fluid detection applications, the feedback may include an indicationof a formation fluid entering the borehole 302 based on vibrationmeasurement data from fluid passing through holes in casing 304 orproduction tubing. Specifically, the vibration sensors 90 may detectevidence that such fluid is entering the borehole at a particular ratebased on impact of the fluid with the coiled tubing string 320.

A method 400 of performing a coiled tubing application using feedback isshown in the flow diagram of FIG. 4. At 402, a coiled tubing string isconveyed along a borehole. The coiled tubing string may be pulled from aspool by a tubing injector and injected into the borehole. The coiledtubing string may include tools to perform a particular coiled tubingapplication and vibration sensors to measure characteristics ofvibrations traveling within the coiled tubing string during the coiledtubing application. The tools, along with a supervisory sub, may make upthe coiled tubing bottomhole assembly.

At 404, vibration measurement data is obtained based on vibrationswithin the coiled tubing string. For example, the tools, supervisorysub, or data processing system may include one or more processorscoupled to the vibration sensors, and the one or more processors may becoupled to memory to record the vibration measurement data. Thevibration measurement data may include characteristics of the vibrationssuch as frequency and amplitude and may also be obtained as tri-axialvibration component measurements (axial vibration, torsional vibration,and a lateral vibration). The vibration measurement data may be obtainedfrom vibrations anywhere along the coiled tubing string including thebottomhole assembly. For different coiled tubing applications, vibrationmeasurement data from different locations will be relevant.

In one embodiment, obtaining vibrations in this manner may includerecording a baseline of vibration data, e.g. over the course of asuccessful coiled tubing operation. Thus, future analysis indicative ofabnormal conditions may be ascertained with a greater degree ofprecision by comparing the newly obtained vibration measurement datawith the baseline.

At 406, feedback is provided, during the coiled tubing application,based on the vibration measurement data. In at least one embodiment, thevibration measurement data is processed to determine the status of thecoiled tubing application. For example, the vibration measurement datais compared with the vibration profile for the particular coiled tubingapplication. The profile may include at least one threshold or range offrequency, amplitude, or average energy associated with each sensor thatmeasures vibrations within the coiled tubing string. If the data iswithin the ranges of the profile, at 408, then a normal status feedbackmay be reported and the method may end.

If the data is not within the profile, at 408, then an abnormal statusis reported along with relevant information about the vibration sensorthat is outside of the profile, and in at least one embodiment,suggested solutions based on the characteristics of the abnormality. At410, a mechanical controller is used to adjust a variable element of thecoiled tubing application based on the feedback. The variable elementmay be continuously adjusted based on the feedback until the vibrationmeasurement data conforms to a profile associated with the coiled tubingapplication. Adjusting the variable element may include adjusting thevariable element of the coiled tubing application automatically based onthe feedback, i.e. without human input.

For example, the coiled tubing application may include freeing a stucktool, the feedback may include an indication of movement in the tool,and the variable element may include force on the coiled tubing string,flow rate of fluid pumped through the coiled tubing, or composition ofthe fluid pumped through the coiled tubing. The mechanical controllerthat adjusts the variable element may include a coiled tubing injector,a valve, or a fluid mixer respectively.

As another example, the coiled tubing application may include clearingdebris using a tool, the feedback may include an indication of jettingperformance of the tool, and the variable element may include flow rateof fluid pumped through the coiled tubing or composition of the fluidpumped through the coiled tubing. The mechanical controller that adjuststhe variable element may include a valve or a fluid mixer respectively.

In at least one embodiment, a method of performing a coiled tubingapplication using feedback includes conveying a coiled tubing stringalong a borehole and obtaining vibration measurement data based onvibrations within the coiled tubing string. The method further includesproviding, during the coiled tubing application, feedback based on thevibration measurement data. The method further includes using amechanical controller to adjust a variable element of the coiled tubingapplication based on the feedback.

In another embodiment, a feedback system for a coiled tubing applicationincludes coiled tubing string. The system further includes a vibrationsensor coupled to the coiled tubing string. The vibration sensormeasures vibrations within the coiled tubing string. The system furtherincludes one or more processors. The one or more processors obtainvibration measurement data from the vibration sensor and providefeedback during the coiled tubing application based on the vibrationmeasurement data. The system further includes a mechanical controller,wherein the controller enables adjustment of a variable element of thecoiled tubing application based on the feedback.

The following features may be incorporated into the various embodiments.Feedback may be continuously provided, over a period of time, based onchanging vibration measurement data resulting from adjusting thevariable element. The variable element may be continuously adjustedbased on the feedback until the vibration measurement data conforms to aprofile associated with the coiled tubing application. The profile mayinclude at least one threshold of frequency, amplitude, or averageenergy associated with each sensor that measures vibrations within thecoiled tubing string. The coiled tubing application may include milling,the feedback may include the vibration measurement data exceeding anamplitude or frequency threshold, and the variable element may includeforce on the coiled tubing string. The coiled tubing application mayinclude milling, the feedback may include milling efficiency, and thevariable element may include force on the coiled tubing string, bitrotational speed, force on bit, bit type, or flow rate of fluid pumpedthrough the coiled tubing. The coiled tubing application may includefreeing a stuck tool, the feedback may include an indication of movementin the tool, and the variable element may include force on the coiledtubing string, flow rate of fluid pumped through the coiled tubing, orcomposition of the fluid pumped through the coiled tubing. The coiledtubing application may include clearing debris using a tool, thefeedback may include an indication of jetting performance of the tool,and the variable element may include flow rate of fluid pumped throughthe coiled tubing or composition of the fluid pumped through the coiledtubing. The coiled tubing application may include perforation, thefeedback may include an indication that a perforation gun has not fired,and the variable element may include flow rate of fluid being pumpedthrough the coiled tubing or depth of a perforation tool in theborehole. The coiled tubing application may include formation fluiddetection, and the feedback may include an indication of a formationfluid entering the borehole based on vibration measurement data fromfluid passing through holes in borehole casing or production tubing. Thecoiled tubing application may include extended reaching, and thevariable element may include force on the coiled tubing string or flowrate of fluid pumped through the coiled tubing. Obtaining vibrationmeasurement data may include obtaining vibration measurement data basedon vibrations within a bottom-hole assembly of the coiled tubing string.Adjusting the variable element may include adjusting the variableelement of the coiled tubing application based on the feedback withouthuman input. The coiled tubing string may include a bottom-holeassembly, and the processor may adjust the variable element based on aspeed of the bottom-hole assembly as well as the feedback. The vibrationsensor may include a tri-axial vibration sensor. The vibration sensormay include a piezoelectric accelerometer. The coiled tubing string mayinclude a bottom-hole assembly, and the processor may obtain vibrationmeasurement data based on vibrations within the bottom-hole assembly.The one or more processors may continuously provide, over a period oftime, feedback based on changing vibration measurement data resultingfrom adjusting the variable element. The controller may continuouslyadjust the variable element based on the feedback until the vibrationmeasurement data conforms to a profile associated with the coiled tubingapplication.

Numerous variations and modifications will become apparent to thoseskilled in the art once the above disclosure is fully appreciated. Theensuing claims are intended to cover such variations where applicable.

What is claimed is:
 1. A method of performing a coiled tubingapplication using feedback comprising: conveying a coiled tubing stringalong a borehole; obtaining vibration measurement data based onvibrations within the coiled tubing string; providing, during the coiledtubing application, feedback based on the vibration measurement data;and using a mechanical controller to adjust a variable element of thecoiled tubing application based on the feedback.
 2. The method of claim1, wherein the coiled tubing application comprises milling, the feedbackcomprises the vibration measurement data exceeding an amplitude orfrequency threshold, and the variable element comprises force on thecoiled tubing string.
 3. The method of claim 1, wherein the coiledtubing application comprises milling, the feedback comprises millingefficiency, and the variable element comprises force on the coiledtubing string, bit rotational speed, force on bit, bit type, or flowrate of fluid pumped through the coiled tubing.
 4. The method of claim1, wherein the coiled tubing application comprises freeing a stuck tool,the feedback comprises an indication of movement in the tool, and thevariable element comprises force on the coiled tubing string, flow rateof fluid pumped through the coiled tubing, or composition of the fluidpumped through the coiled tubing.
 5. The method of claim 1, wherein thecoiled tubing application comprises clearing debris using a tool, thefeedback comprises an indication of jetting performance of the tool, andthe variable element comprises flow rate of fluid pumped through thecoiled tubing or composition of the fluid pumped through the coiledtubing.
 6. The method of claim 1, wherein the coiled tubing applicationcomprises perforation, the feedback comprises an indication that aperforation gun has not fired, and the variable element comprises flowrate of fluid being pumped through the coiled tubing or depth of aperforation tool in the borehole.
 7. The method of claim 1, wherein thecoiled tubing application comprises formation fluid detection, thefeedback comprises an indication of a formation fluid entering theborehole based on vibration measurement data from fluid passing throughholes in well casing or production tubing.
 8. The method of claim 1,wherein the coiled tubing application comprises extended reaching andthe variable element comprises force on the coiled tubing string or flowrate of fluid pumped through the coiled tubing.
 9. The method of claim1, wherein obtaining vibration measurement data comprises obtainingvibration measurement data based on vibrations within a bottom-holeassembly of the coiled tubing string.
 10. The method of claim 1, whereinadjusting the variable element comprises adjusting the variable elementof the coiled tubing application based on the feedback without humaninput.
 11. The method of claim 1, further comprising continuouslyproviding, over a period of time, feedback based on changing vibrationmeasurement data resulting from adjusting the variable element.
 12. Themethod of claim 11, further comprising continuously adjusting thevariable element based on the feedback until the vibration measurementdata conforms to a profile associated with the coiled tubingapplication.
 13. The method of claim 12, wherein the profile comprisesat least one threshold of frequency, amplitude, or average energyassociated with each sensor that measures vibrations within the coiledtubing string.
 14. A feedback system for a coiled tubing applicationcomprising: coiled tubing string; a vibration sensor coupled to thecoiled tubing string, wherein the vibration sensor measures vibrationswithin the coiled tubing string; and one or more processors, wherein theone or more processors: obtain vibration measurement data from thevibration sensor; and provide feedback during the coiled tubingapplication based on the vibration measurement data; and a mechanicalcontroller, wherein the controller enables adjustment of a variableelement of the coiled tubing application based on the feedback.
 15. Thesystem of claim 14, wherein the coiled tubing string comprises abottom-hole assembly, and wherein the processor adjusts the variableelement based on a speed of the bottom-hole assembly as well as thefeedback.
 16. The system of claim 14, wherein the vibration sensorcomprises a tri-axial vibration sensor.
 17. The system of claim 14,wherein the vibration sensor comprises a piezoelectric accelerometer.18. The system of claim 14, wherein the coiled tubing string comprises abottom-hole assembly, and wherein the processor obtains vibrationmeasurement data based on vibrations within the bottom-hole assembly.19. The system of claim 14, wherein the one or more processorscontinuously provide, over a period of time, feedback based on changingvibration measurement data resulting from adjusting the variableelement.
 20. The system of claim 19, wherein the controller continuouslyadjusts the variable element based on the feedback until the vibrationmeasurement data conforms to a profile associated with the coiled tubingapplication.